Method of making thread-cutting dies



Aug. 19, 1930. o. w. BERG 1,773,471

' METHOD oF IAKING THREAD cu'r'rING mins A Filed July 21. 192s Patentedug.' 19, 193@ *Uni-ran stares swam oscar. w. sans. lor soMEBvrLLE,Meissner-mesme METHOD OF MAKING THREAD-CUTTING DIES Application iii-eaJuly ai,

lif not impossibleto produce solid cutting dies smaller than about 1/2dies with a clearance. My present invention provides a solid threadcutting die having a clearance at the heel of the cuttiiigsurface. Thedies embodying my "invention, therefore, have the chief advantages ofthe di-es with loose cutters but can be made in accordance with mynovelv method liereindes'cribed much more cheaply.

The invention will be fully understood from the following descriptionwhen taken in connection with the accompanying drawings and lthe novelfeatures thereof will be clearly pointed out and defined in the claim atthe close of this specification.

In the drawings:

Fig. 1 is a View in perspective of a blank.

Fig. 2 shows the blank with the preliminary threading.

Fig. shows the blank with a master tap in place.

"Fig: 4 is a horizontal section of the master tap and blank shown inFig. Fig. 5 shows theblank being compressed onto-the master tap. f Y

Fig. 6 shows the completed cutter.

VReferring to the drawings, l first prepare a blank 11 as shown in Fig.1.' This blank has four holes 12 drilled'aroiind and com-- municatingwith a central hole 13 to provide four lands 14 between the holes 12.`The blank as thus prepared is tapped out in the ordinary manner toprovide screw thread edges 15 as shown in Fig. f2. These edges 15 formvarcs of a circle having the axis ofthe cutter as a center. Up to thispoint the procedure is the same as has heretofore been ypracticed inmaking ordinary solid cutters.

If the cutter is hardened in this form no clearance is provided betweenthe heel of each land ieee. seifiai Ne. 294,41?.

and the work. If clearance isfnot provided the friction of the landenthe work prevents satisfactory operation of. such tools.`

To obviate this difliculty. I providea hardened master form 16 havingspaced project-L ing portions 17V shaped complementary vto pro-duced,that is, having edges which ineline or taper away from a circle havingthe axis oftheform `as a center. I then `place this master form inposition in the ythe shape of thev lands of the cutter to be centralhole 13 with. the 'projectingl .por- `i tions opposite` the lands withinthe central hole of the blank asA shown in Figs. 3, 4r and 5. TheVrelation of the parts at thisl time will be clearly seen from Fig. 4where the clearance between the Vland 14 and the iv correspondingportion of` the master form is indicated by a. The blank and the masterform while thus relatively positioned are y placed in a press indicateddiagraininatically `in Fi g. 5 and pressure applied simultaneously toall four sides of the blank. `This pressure is great enough to cause themetal to flow and toffill the spaces l-ct between the ends of. the landsand the sides Aof theinaster forni. n

This gives to the lands the shape determined by the shape of themastervform. n YThis shape is clearly seen in Fig. 6 where it will beseen that each of the lands y14 has aclearance between the leading orcutting edge of the land.

and theheel or rear edge thereof. The nias-v ter form is then removedand the cutter suitably hardened. The invention makes it possible toproducea solid cutter having the ad vantages of the loose or separatebit cutter' at an expense only slightly greater than tI of the ordinarysolid cutter.

1t is to be understood that the invention is y of the claimhereto-appended as considered, in

hat..

View of the prior art and the requirements thereof.

What I claim is:

The method of making a thread cutting die which comprises preparing ablank having lands within a central hole, threading said lands,inserting therein a master form having ashape complement-arg7 to thesha-pe of the cutter to be produced, compressing the blank to cause thelands to take shape complementary to the shape of the master form,removing the form, and hardening the shaped blank. Y

In testimony whereof I aiix my signature.

OSCAR Y W. BERG.

